Some background: we have many thousands of products with size variants (example: a product's ID may be FWAP1069 with size variants FWAP0169L, FWAP0169X, etc). 

At the moment we are doing test uploads to get all of our processes in place. Attribute templates have been created. We have a workable Inventory Import sheet that we continue to refine for everything to include in our bulk csv imports. 

Our desire is to bulk-assign our own size variant names to what Odoo uses as its Internal Reference for variants in the initial upload of a product, as having to perform all the steps I will describe below is not feasible. 

I think the best way for anyone to understand what we are trying to do is to share how we are moving toward the goal:

1. Used our Inventory Import sheet to create a product FWAP0169 with all its size variants (S,M,L,X,2X)
2. This creates the size variants in Odoo but leaves blank the 'Internal Reference' field (ex: FWAP0169X) when viewing in Inventory > Product Variants
3. Going into each entry manually to update Internal Reference is not the ideal, so I wanted a way to bulk upload our child skus as the Odoo internal references for each variant...
4. In Odoo > Inventory > Product Variants I selected all products. Then used the method described here (link apparently not allowed without 20 karma points, but the Stack Overflow post is titled "Odoo - Bulk Update Product Variant Internal ID") to create an export template for this purpose...
5. ... I opened the sheet and stripped out all columns except id, display name, and default code. The 'default code' column was empty and is where I pasted our child skus to correspond with the display names (ex: FWAP0169X correctly corresponded with 'Example Product (X)'. Then I deleted the display name column and exported the sheet to include only the necessary columns of 'id' and 'default code'
6. I uploaded the sheet to Odoo > Inventory > Product Variants and it correctly assigned our variant sku names into the Internal Reference field for each size variant for the product.

Hopefully this is a clear enough description of what we hope to achieve. 

The most helpful answers would include a straightforward explanation of what column headers to use on our Inventory Import sheet to push the Internal Reference for each size variant.

Any insight is greatly appreciated. Thanks!